1) Regarding the open plan layout, the sprinklers are there to protect the people in the inner-rooms, so more the fool them if they don't maintain the system. They are masters of their own destiny with this regard, so long as they are made aware the reason for the sprinkler system being there.
2) The fire service are unable to enforce anything within the domestic areas, so we can not force these people to maintain the system.
3) Simply not having the system maintained would not automatically lead to an offence, so we can not prosecute someone simply for not maintaining it either. (If we had proof that the system was turned off or faulty, then prosecution would then be possible)
4) The RP simply does not have control, so they cannot truly be held accountable.
However, should a fire occur, and the non-maintenance of the sprinkler system means that the smoke control system is overpowered, and relevant persons are put at risk of death/serious injury, then we can prosecute the flat owner for failing to comply with article 17(4). This would be done under 32(10). We could also take the RP on, but if they have made every effort to remedy the issue, it would be pointless as they have a valid defense.
32 (10) Where the commission by any person of an offence under this Order, is due to the act or default of some other person, that other person is guilty of the offence, and a person may be charged with and convicted of the offence by virtue of this paragraph whether or not proceedings are taken against the first-mentioned person.
Unfortunately I believe that it is a situation where we essentially have to wait for the actual offence to happen via a fire occurring before we can do anything.